At the Korean Shoulder and Elbow Society meeting
Dr Kenneth Cutbush presented research from colleagues at the Korean Shoulder and Elbow Society Annual Scientific Meeting in Seoul. The work, led by Dr Wolbert van den Hoorn, examines how the nervous system controls the deltoid muscle.
Why the deltoid is the focus
Rotator cuff tears become more common with age; published estimates suggest a substantial proportion of people have one by their seventies, many of them without symptoms. For those who do have symptoms, the pain can affect sleep, work and recreation.
Reverse total shoulder replacement has substantially changed what can be offered to people with end-stage shoulder conditions, including irreparable cuff tears, because it works through the deltoid rather than the cuff. Many people find that after surgery they stop thinking about the shoulder, which is generally the aim. Individual results vary.
Deltoid function is therefore central to how well a reverse replacement works, and the deltoid sometimes underperforms after surgery. Understanding why is the point of this research.
What the healthy-volunteer study found
The team began with healthy volunteers, using electromyography (EMG). That study reported an average of 18 motor units per deltoid, coordinated by three overlapping neural drives, one each for the anterior, lateral and posterior parts of the muscle.
The planned next step is to study deltoid function in patients who have had a reverse replacement, using the same technique. The hope is that the findings could inform surgical planning or post-operative rehabilitation.
The team
Ella Hill, Fred Dupuis, Francois Hug, Kylie Tucker, Wolbert van den Hoorn, Ashish Gupta and Mark Ross.
Related information
See our reverse total shoulder replacement and rotator cuff tear pages, and our posts on research into deltoid function and the Driving the Deltoid project.